Limekiln and method of burning lime



May 3 1927.

A. E. TRUE SDELL LIME KILN AND METHOD OF BURNING LIME Filed April 23. 1923 Fig. 2.

Inventor. Arthur E.True5dell ymwkw burning limestone in vertical kilns.

' the Patented May 3, 1927.

UNITED STATES.

PATENT OFFICE.

ARTHUR E. TRIIESDELL, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR OI bNE-EALF TO DOHERTY RESEARCH COMPANY, OF NEW YORK, N. Y., A CORPORATION OI Dm- WARE.

LIMEKILN AND METHOD OF BURNING LIME.

Application filed April 23, 1923. Serial No. 633,819.

This invention relates to the burning of lime and one of the objects of the invention is to rovide a novel vertical lime kiln in which limestone can be successfully and etiiciently burned with a fuel which develops a temperature in the products of combustion much higher than that which is suitable for burning lime, and another object of the. invention is to provide a novel process of burning limestone by whidch fuel of this nature can be efficiently use For the most efficient burning of limestone it is desirable that the temperature of the products of combustion to which the limestone is subjected should be adapted to the chemical composition of the limestone.

Since such chemical composition varies greatly in various limestones used for pro-' ducing lime, especially in regard to the content of magnesium carbonate, there is considerable range'in the proper temperature for burning various kinds of limestone. In no case however should the temperature of the products of combustion be much higher than 900 degrees centigrade, at which temperature calcium carbonate is freely dissociated under atmospheric pressure.

The temperature of the products of combustion resulting from the burning of wood as .fuel is in the neighborhood of .1000 degrees centigrade and for this reason wood has been extensively used as the fuel for Owin to the present increasing scarcity of wood 'however, other fuels for this purpose are in more or less demand, but one difficulty which arises when coal, oil or similar fuels are burned is that the products of combustion produced by the burning of such fuel is much too high to produce a good quality of lime.

One method which has been heretofore suggested for reducing the temperature of products of combustion where coal is used for fuel has been to provide means for delaying the combustion by introducing waste kiln gases beneath the grate for the purpose of diluting the air used for producmgzicombustion. While this method results in reducing the temperature of the roducts of combustion yet it has the disa vantage that it makes the combustion less etlicient ;with the result that the fuel is not burned economically.

In myinvention I have provided an ap paratus and process by which fuel such as coal or oil can be burned in the most etlicient manner while at the same time the products of combustion are delivered to the limestone at the required temperature necessary for etlicient burning of the lime.

I accomplish this end by burning the fuel in the most efiicient manner with the result that products of combustion are develo ed which are at a temperature in excess of t at required for efficiently burning lime and then before introducing the high-temperature products of combustion into the vertical shaft of the kiln I reduce thetemperature of said productslof combustion by diluting them with waste gases withdrawn from the have given up to the limestone in passing through the kiln and the mingling of them in the proper proportion with the hot products of combustion serves to reduce the temperature of the latter to that which is desired for the most efiicient burning of the limestone.

One way of accomplishing this is by providing a recirculation fan which is constructed to withdraw the waste gases from the upper end of the shaft of the kiln and introduce them into the furnace beyond the point of combustion where they will commingle with the products of combustion before the latter are delivered to the shaft of the lime kiln.

My process makes it possible to use successfully ulverized coal, oil or other similar fuels or the burning of limestone.

In order to give an understanding of the invention I have illustrated in the drawings some selected embodiments of the inven-- tion which willnow be described after which the novel features'will be pointed out in the appended claims.

Fig. l is a vertical sectional view of a lime kiln embodying my invention, said section being taken on the line 1-1, Fig.2;

Fig. 2 1s a side view of Fig. 1;

Fig. 3 is a top plan View;

Fig. 4 is a section on the line 44, Fig. 3;

Fig. 5 shows a different embodiment of the invention.

In the drawings 1 indicates the cupola portion of a vertical kiln which may be of any suitable construction and which is shown as having at its upger end a filling hop r 2 when most eflicientl-yburned produce prod: I ucts of combustion at a temperature. considerably higher than that required for eflicient burning of the limestone. The particular furnace illustrated in the drawings is one designed to burn pulverized coal and it is provided with a combustion, chamber 5 into a which the pulverized coal is delivered under pressure through nozzle 6. The coal burns as .fast as it is, delivered from the nozzles and the furnace is designed to admit the proper amount of air with the coal or otherwise so that complete combustion of the coal will take place in the chamber 5. The roducts. of combustion which are thus pro-- duced have a temperature of perhaps 1900 or 2000 degrees centigrade. .This is much too high for the' efficient burning of the limestone.

My invention contemplates the reducing of this excessivelyhigh temperature. of the.

products of combustion by diluting them with waste gases withdrawn from the stack- 1. This ma be accomplished in various ways. In igs. 1 to 4 I have illustrated a recirculation fan 7 which is connected by an inlet duct 8 to the upper end of the' Qupola as shown at 9; the exhaust or dis from the. fan 7' delivering into a pipe r 10 w%ch is shown as-provided with the two branches 11 that lead to two manifold cham bars 12 one for each of the furnaces 4. Each therefore, operates to withdraw waste from the top ofthe kiln 1 and to de ive'r" 'chamber 12. is provided with ports 13 that open into the combustion chamber 5 in the rear of the point of combustion. The fan 7, ses

' be commingled with the products of 'combus tion but will not in any way interfere with the combustionof the fuel. The. waste gases which are withdrawn from the to of the kiln are, of course, at a relatively ow temperature because. of the heat which has been given up by them to, the limestone during eir passage upwardly through the kilm.

The commingling oi these relatively cool gases with the excessively hot products of] d combustion reduces the temperature of. the latter andv by thus diluting the products of, combustlon to. the proper amount the temr 1 This same regulationof} the; temperature can also be secured byvarying the.

perature thereof may be. to" that, which is most. efiicient. for of tin limestone.

The fan 7 may be operated in any? suitable way and by varying the speed at. which the II fan operates or by the. use. of dam rs the amount of waste gases. delivered to. t nets of combustion can be'varied and t onfore, the burnedfproducts of combustion on be brought to. theright. temperature for 3.8. II efiicient burning; of the, limestone,

In Figs. 1 and 2; I have illustrated an exhaust fan 14 for withdrawing theygpsos from the kiln and roduci'ng proper therein and at15j have. indicated a. I eter by which the temperature. of the gases can bedetermined, 1'' have. also: shown a damper 31 in the, pipe 10 for eontrolilg the recirculation current... In the o.

of the device the'exhaust. fan may be. m an as to produce the. necessary draft through tb kiln. and the amount of recirculation offwash gases will be varied as me to lnlir tain the pro r temperaturei nt If.

.it is found .t at the temperature. ofthe walk gases delivered from the exhaust; fan 14 stoo high; thus: indicating two-high I perature in the kiln, then thQnMQQl-T 81 may be opened-to a greater am, am a: v to. provide a. greater amount of Iii of the waste gases, and a, greaterdilhtionofi the. products; of combustion.v This: willv duce the temperature oi the products; of 0mm bustion. 0n the other if it. is'fimnd" that the temperature in the, kiln. is; too lbw HI thusindicating too at adilutibn of products of combustion than the; may be closed 'somewhat; thus: reducing than amountof recirculation] the amount of dilutionfof the; products'oi ma bustion. By thus regulating theaimuntd: recirculation the temperature: of the gum delivered to: the. limestone canzba centroid so as to produce mostefici'ent, burning of Hit limestone. I!

speeds'of the fans/7" 14:

It will, be noted that with this. arrango-- ment the-fuel is; burned so as to: premium m completecombustijon and thus a. dbgree of efliciency', but notwi v hiburning of th 1 fuel inv way m products of. combustion, which have gether too high atemperature for burning the limestone, yet the efi'ciont 1 ing of the limestoneuls produced method of dilutingtheexoeaaivelynets of g-m from the kiln'. I II My invention, M

e [of efli'ci" fu l zfs well as-a of in the burning'qoftho-limestone...

InJig, 5,. a. little difiemnt: I

is shown wherein a sin 1e fan is used for both recirculation and ex aust purposes. In this construction the single fan is indicated at 16, the inlet of the fan-communicating with the upper end of the cupola 1 and the exhaust from the fan connecting with a pipe 17 which is branched, one branch 18 I leading to the two branches 12 and the other v the ticuwuel, as oil may be used instead of pulverized coal or the furnace may be arranged to burn coal on a grate with just the right proportion of air to secure complete combustion. The invention contemlates the use .of any fuel which when urned most efliciently produces products of combustion at a tem erature in excess of that which is required or best operation of the lime kiln and the reduction of the temperature of such excessively hot products of combustion to that which is most efiicient in burning the limestone by diluting such products of combustion with waste gases withdrawn from the kiln.

' While, therefore, I have described some embodiments of the invention I do not wish to be limited to the constructional features shown. Furthermore I desire to state that while I have illustrated the invention as adapted to theburning of lime yet the in-- vention is' not necessarily confined to this use and may be used for other purposes.

I claim:

fuel under conditions to produce products of combustion at a temperature in excess of that required for the eflicient burning of.

bustion and waste 1. In a lime kiln a combination with. the vertical kiln, of a furnace arranged to burn" 'name to this specification.

limestone and to deliver such products of combustion to the kiln, and means to with draw waste gases from the kiln and introduce them into the furnace between the point where the combustion takes place and where the roducts of combustion are delivered to the kiln.

2. The method of burning limestonein a kiln having a stack containinglimestone and also having an external furnace, which consists in burning fuel in the furnace in such manner as to produce products of combustion at a temperature in excess of that required for the efiicierit burning of limestone, withdrawin waste gases from the top of the stack an commingling said gases with the products of combustion at a point beyond that at which said. roducts of combustion are formed and be ore they are delivered -to the stack, thereby to reduce the v temperature of said products of combustion to t at required for efiicient burning of the limestone, and then introducing to the stack the commingled roducts of combustion and waste ases at t e reduced temperature.

3. e method of burning limestone in a kiln having a stack containing limestone,

which consists in burning fuel exterior to the stack under conditions to produce products of combustion at a temperature in' excess of that required for the efiicient burning of-limestone, withdrawing from the top of the stack; waste said waste gases with the roducts of com-- bustion exterior to the stac and at a point beyond that at which said products of combustion are formed, whereby the temperature of the products of combustion is reduced to that required for ellicient burningof the limestone, and then introducing to the stack the commingled products of comgases at the reduced temperature. v

In testimony whereof I have signed my ARTHUR E. TRUESDELL. I

ases which have atemperature less than t at required for the efii-" cient burning of limestone, commingling '8 

